Inductive power supply system with multiple coil primary

ABSTRACT

An inductive power supply including multiple tank circuits and a controller for selecting at least one of the tank circuits in order to wirelessly transfer power based on received power demand information. In addition, a magnet may be used to align multiple remote devices with the inductive power supply. In one embodiment, different communication systems are employed depending on which coil is being used to transfer wireless power.

This application claims the benefit of U.S. Provisional Application No.61/036,459 filed Mar. 13, 2008.

BACKGROUND OF THE INVENTION

The present invention relates to inductive coupling and moreparticularly to systems and methods for providing multiple ranges ofinductive power.

Systems for providing wireless power using the principles ofelectromagnetic inductive have been available for many years.Conventional systems have met with limited success as a result ofpractical limitations on pre-existing inductive technology. For example,to provide reasonably efficient operation, conventional inductivesystems typically require close and precise alignment between theprimary coil and the secondary coil, as well as a high degree ofcoordinated tuning between the electronics in the inductive power supplyand the electronics in the remote device. These problems are complicatedby the fact that different remote devices may require vastly differentamounts of power. For example, a cell phone is likely to have differentpower requirements than a laptop or a kitchen appliance.

Some advances have been made that allow an inductive power supply toadjust and account for some differences between remote devices. U.S.Pat. No. 6,825,620 to Kuennen et al discloses an inductive power supplysystem that has the ability to adjust its operation to correspond withthe operating parameters of various loads. U.S. Pat. No. 6,825,620 toKuennen et al, which is entitled “Inductively Coupled Ballast Circuit”and was issued on Nov. 30, 2004, and is incorporated herein byreference. U.S. patent application Ser. No. 11/965,085 discloses aninductive power supply system that has the ability to identify theremote device and its operating parameters. U.S. patent application Ser.No. 11/965,085 to Baarman et al, which is entitled “Inductive PowerSupply with Device Identification” and was filed on Dec. 27, 2007, andis incorporated herein by reference. Although these are markedimprovements over pre-existing systems, there is, in some applications,a desire for even greater flexibility. In some applications, thereexists a desire for a single inductive power supply that is capable ofproviding multiple ranges of power.

SUMMARY OF THE INVENTION

The present invention provides an inductive power supply system andassociated method that identifies a power class of a remote device andprovides inductive power as a function of that power class. In order toprovide power as a function of power class, the inductive power supplyincludes a primary coil assembly with multiple coils. Each coil iscapable of being selectively energized to produce a range of inductivepower associated with a different power class. The inductive powersupply system provides multiple ranges of power to remote deviceswithout physical electrical contact.

In one embodiment, the present invention includes an inductive powersupply having a controller, a coil selector circuit and a coil assembly.In this embodiment, the coil assembly includes a low power coil, amedium power coil and a high power coil. Each remote device iscategorized as a low power class, medium power class or high power classdevice. The controller and coil selector circuit operate to energize aselected coil. In general, the low power coil is energized to power lowpower class devices, the medium power coil is energized to power mediumclass devices and the high power coil is energized to power high powerclass devices. In some applications, the low power coil may be used forauthentication, identification or communication, even in medium powerclass and high power class devices. The inductive power supply mayimplement techniques for tuning the power provided by the selected coil.For example, each coil may be adaptive and capable of having itsresonant frequency adjusted. Further, the operating frequency or otheroperating characteristics of the inductive power supply may vary.

In operation, the remote device communicates power demand informationwith the inductive power supply, such as the remote device power class.In one embodiment, the low power coil, when driven, produces a timevarying magnetic field. When the secondary circuit is moved in proximityto the driven low power coil, the secondary circuit forms a mutualinductance with the low power coil. The low power coil's magnetic fieldpasses through and energizes the secondary coil. This provides power tothe secondary allowing a power class signal to be transmitted andauthenticated starting the power control sequence at the appropriaterange of power by selecting the appropriate coil.

One benefit of an inductive power supply having a coil assembly withmultiple coils is that a single hot spot may deliver low, medium andhigh power to a remote device. This reduces the need to have aninductive power supply that powers low power devices, a separateinductive power supply to power medium power devices and a separateinductive power supply that power high power devices. Further, energysavings may result because higher power devices may use a lower powercoil during lower power consumption periods. Additionally, lower powerdevices may draw power from a higher power coil in order to gain spatialfreedom.

These and other objects, advantages, and features of the invention willbe readily understood and appreciated by reference to the detaileddescription of the current embodiment and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an inductive power supply system inaccordance with an embodiment of the present invention.

FIG. 2 is a block diagram of a primary circuit of one embodiment.

FIG. 3 is a block diagram of a secondary circuit of one embodiment.

FIG. 4 is a schematic diagram of a tank circuit of one embodiment.

FIG. 5 is a schematic diagram of an inductive power supply system of oneembodiment.

FIG. 6 is a schematic diagram of a tank circuit of one embodiment.

FIG. 7 is a schematic diagram of an inductive power supply system of oneembodiment.

FIG. 8 is a circuit diagram of a switching circuit and tank circuit ofone embodiment.

FIG. 9 is a flowchart showing the general steps of a method for poweringa remote device.

FIG. 10 is a functional block diagram of a primary circuit of oneembodiment.

FIG. 11 is a functional block diagram of a secondary circuit of oneembodiment.

FIG. 12 is a functional block diagram of a primary circuit of oneembodiment.

FIG. 13 is a functional block diagram of a secondary circuit of oneembodiment.

FIG. 14 is a schematic diagram of an inductive power supply system ofone embodiment.

FIG. 15 shows a cross section of litz wire.

DESCRIPTION OF THE CURRENT EMBODIMENT

I. Overview

In an exemplary embodiment of the inductive power supply system of thepresent invention depicted in FIG. 1 and designated 100, the inductivepower supply system includes an inductive power supply 102 and a remotedevice 104. The inductive power supply includes a primary circuit 103having a primary coil assembly 101 capable of generating multiple rangesof power. The remote device 104 includes a secondary circuit 105 havinga load 106. The secondary circuit 105 of the remote device includespower demand information that may include a power class. The powerdemand information may be transmitted to the inductive power supply 102in order to facilitate power transfer at an appropriate range of power.In response to the power demand information, the primary circuit 103selects an appropriate coil of the primary coil assembly 101 over whichto transfer power to the remote device 104. In one embodiment, the coilis selected at least in part as a function of the power class of theremote device. The ability to select different ranges of power with asingle inductive power supply allows power transfer to devices withvastly different power demands.

The invention is described in the context of a coil assembly 101 withthree coils that provide three different ranges of power that correspondrespectively to three power classes. However, in some embodiments, thecoil assembly may includes additional or fewer coils, therebyrespectively increasing or decreasing the number of different ranges ofpower, and therefore number of power classes, that may be provided. Thatis, in the described embodiments, there is a one to one mapping betweenthe number of ranges of power and the number of power classes. However,that need not be the case. In scenarios where there are more powerclasses than there are coils, multiple power classes may be mapped tothe same coil. And vice versa when there are more coils than powerclasses. In some embodiments, there may be some overlap between powerclasses or the ranges of power provided b the different coils.

In some applications, devices may demand different amounts of power atdifferent times. An example of this is demonstrated during a method oftransferring power. The primary circuit 103 of the inductive powersupply 102 periodically transmits power using a lower power coil. Aremote device 104 that receives that power uses it to transmit powerdemand information to the inductive power supply 102. The inductivepower supply uses the power demand information to select the appropriatecoil of the coil assembly 101 for power transfer, which may be adifferent coil than the one used during the initialization procedure.

II. Inductive Power Supply System

One embodiment of an inductive power supply system in accordance withthe present invention is pictured in FIG. 5, and generally designated500. The inductive power supply system 500 depicts an inductive powersupply 503 and a remote device 504. Although depicted generically, theremote device 504 could be essentially any type of device that iscapable of communicating, including allowing the inductive power supplyto detect, power demand information, such as the power class of theremote device.

The inductive power supply 503 may be contained within a housing 501,such as a dedicated housing having a surface 506 on which to place theremote device 504. The size, shape and configuration of the housing 501and surface 506 may vary. Further, the location of the primary coils512, 514, 516 of the coil assembly 502 may also vary with respect to thesurface 506 and with respect to each other. In the FIG. 5 embodiment,the coils 512, 514, 516 are arranged in a planar, concentricconfiguration under surface 506.

In alternative embodiments, such as the embodiment illustrated in FIG.7, the coils 712, 714, 716 may be arranged in vertical alignment andembedded within the side wall 702 of a housing 701 that is shaped as acontainer with a surface 706 on which to place the remote device 704.FIG. 5 and 7 are merely examples of how the housing, surface and coilsmay be arranged. Many other configurations are possible.

Similarities between the remote device secondary coil and the activeprimary coil promote efficient power transfer. For example, thesecondary coil 509 and low power coil 512 are similar in size, shape,number of turns, length and gauge. These similarities make betteralignment possible, which facilitates efficient power transfer.Similarly, medium and high power class devices may have a secondary withcharacteristics similar to the medium and high power coils respectively,which facilitates better power transfer when energizing those coils.

The size of the remote device or secondary coil may help align theremote device in the FIG. 7 embodiment as well. Although not true inevery case, low power class devices tend to be physically smaller, whilehigh power class devices tend to be physically larger in comparison.This means that where the coils are arranged vertically, as in the FIG.7 embodiment, a smaller device has a tendency to align better with thelow power coil 712 while a larger device has a tendency to align betterwith the high power coil 716.

Alignment of the remote device and active primary may be furtherfacilitated by magnetic positioning. In some applications, the inductivepower supply system 500 may incorporate a magnet 510 in the inductivepower supply and a magnet 508 in the remote device to provide magneticpositioning. The inductive power supply system 500 may incorporateessentially any of the features from U.S. Provisional Patent Application61/030,586 filed on Feb. 22, 2008 and titled “Magnetic Positioning forInductive Coupling,” which is herein incorporated by reference. Themagnet may be for use with any combination of low, medium and high powerclass remote devices. Magnetic positioning may be used in some, all orno remote devices. The magnets are optional and need not be provided inthe inductive power supply or remote device.

In some applications, multiple devices may be powered simultaneously bythe inductive power supply, perhaps as best seen in FIG. 14. One simplescenario is where a higher power coil is used to power multiple lowerpower class devices. Because the higher power coil exhibits a largerinductive field that covers more area, there is more space for thedevices to be positioned within. That is, because power efficiency doesnot substantially limit the amount of power a lower power device mayreceive during charging from a higher power coil, the lower powerdevices gain spatial freedom.

It should also be noted that more forgiving loads and devices may use acoil with a power class higher than the remote device power class inorder to obtain benefits in spatial freedom. The devices are poweredusing a higher power coil, but at lower powers based on deviceclassifications and other criteria. In the illustrated embodiment, suchbenefits may be obtained by using the medium power coil 514 or highpower coil 516 with low power remote devices. One example of a forgivingload is a remote control. Typically, a forgiving load can be charged atdifferent rates or with different amounts of power without itsperformance being substantially impaired.

Just as higher power coils can be used with lower power devices in somesituations, so can lower power coils be used with higher power devicesin some situations. Some higher power devices may have standby optionsthat consume less power. In one embodiment, if a higher powered deviceindicates that it needs less power, because, for example, it is enteringstand-by mode, then the lower power coil may be used to provide thatpower. Essentially, although a device may have a general power class,there may be situations where it is beneficial to provide more or lesspower, and those situations may be accommodated using a coil assemblywith multiple coils. This also may result in energy savings.

III. Inductive Power Supply

The present invention is suitable for use with essentially any inductivepower supply that includes a primary circuit 103 that has a primary coilassembly 101 with multiple coils. Accordingly, the circuitry unrelatedto the primary coil assembly 101 in an inductive power supply 102 willnot be described in detail. The primary circuit 103 may includeessentially any circuitry capable of supplying alternating current atthe desired frequency or frequencies. For example, the power supplycircuit 103 may include the resonant seeking circuit of the inductivepower supply system disclosed in U.S. Pat. No. 6,825,620, which isentitled “Inductively Coupled Ballast Circuit” and issued Nov. 30, 2004,to Kuennen et al; the adaptive inductive power supply of U.S. Pat. No.7,212,414, which is entitled “Adaptive Inductive Power Supply” andissued May 1, 2007, to Baarman; the inductive power supply withcommunication of U.S. Ser. No. 10/689,148, which is entitled “AdaptiveInductive Power Supply with Communication” and filed on Oct. 20, 2003 toBaarman; the inductive power supply for wirelessly charging a LI-IONbattery of U.S. Ser. No. 11/855,710, which is entitled “System andMethod for Charging a Battery” and filed on Sep. 14, 2007 by Baarman;the inductive power supply with device identification of U.S. Ser. No.11/965,085, which is entitled “Inductive Power Supply with DeviceIdentification” and filed on Dec. 27, 2007 by Baarman et al; or theinductive power supply with duty cycle control of U.S. Ser. No.61/019,411, which is entitled “Inductive Power Supply with Duty CycleControl” and filed on Jan. 7, 2008 by Baarman—all of which areincorporated herein by reference in their entirety.

One embodiment of a primary circuit of an inductive power supply 102 isillustrated in FIG. 2, and generally designated 200. The primary circuit200 of the illustrated embodiment generally includes a primarycontroller 202, a driver circuit 204, a switching circuit 206, a tankcircuit 208, a wireless receiver 212 and a current sensor circuit 210.

Primary controller 202 controls the driver circuit 204, switchingcircuit 206 and tank circuit 208. The primary controller 202 is capableof processing information, such as power demand information, receivedfrom the remote device 104. The primary controller 202 may includeinternal memory, access external memory or a combination thereof. Thepower demand information may be used to determine which coil of theprimary coil assembly 222 should be energized. In one embodiment, thepower demand information provided by the remote device identifieswhether the device is a low power class, medium power class or highpower class. In an alternative embodiment, the power demand informationprovided by the remote device identifies an amount of power (or a poweradjustment) the remote device would like to receive and the controller202 processes that information to determine which coil to energize. Ifthe power adjustment crosses a power class threshold, a different coilwill be energized. In yet another alternative embodiment, the powerdemand information identifies the remote device and the primarycontroller uses a look-up table to determine which coil to energize.

In one embodiment, the power demand information includes informationregarding minimum, maximum, or both power levels for specific coilselections. The thresholds used to determine which coil to energize mayvary as a function of the power demand information. For example, for oneremote device, the low power coil threshold minimum and maximum may beone value, but for a different remote device, the low power coilthreshold minimum and maximum may be different values. There may besituations where for one remote device it is appropriate to use the lowpower coil to transmit a certain amount of power and for another remotedevice it is appropriate to use a medium power coil to transmit thatsame amount of power. The power demand information stored in the remotedevice may be based on capabilities and design expectations among otherthings.

The primary controller 202 may be programmed with additional features.For example, in one embodiment, the primary controller 202 is programmedto identify remote devices using the inventive principles described inU.S. Ser. No. 11/965,085, which was previously incorporated byreference. For example, the remote device ID may include power demandinformation. Alternatively, power demand information may be accessedusing the remote device ID as a key to a look up table on the inductivepower supply 102.

Essentially any type of driver 204 and switching circuit 206 may beused. The switching circuit 206 in the current embodiment is implementedas a pair of switches that form an inverter that converts DC to AC.

The tank circuit 208 of FIG. 2 includes a coil selector circuit 220 anda primary coil assembly 222 with multiple coils. The coil selectorcircuit 220 is capable of energizing one or more of the multiple coilsof the coil assembly 222. FIG. 4 illustrates selecting between multipleseparate coils, FIG. 6 illustrates selecting between multiple taps of asingle coil, and FIG. 15 illustrates selecting between multiple segmentsof a single coil. The illustrated embodiments are merely examples, anycombinations of separate coils, multiple taps, and multiple segments maybe used to provide a variety of different multiple coil configurationoptions. In one embodiment, the controller 202 instructs the coilselector circuit 220 on which coil to energize. In the illustratedembodiment, the primary coil assembly 222 includes three coils: a lowpower coil, a medium power coil and a high power coil. In alternativeembodiments, the primary coil assembly 222 includes additional or fewercoils. In some applications, the coils of the primary coil assembly 222may be made of Litz wire. In other embodiments, the coils may be anycombination of copper, LITZ, PLITZ, FLITZ, conductive ink or any othermaterials that have coil properties. The characteristics of each of thecoils may vary from application to application and coil to coil. Forexample, the number of turns, size, length, gauge, shape andconfiguration of each coil may vary. In one embodiment, the low powercoil has approximately 10 strands of LITZ wire, the medium power coilhas approximately 50 strands of LITZ wire and the high power coil hasapproximately 138 strands of LITZ wire. In one embodiment, the soledifference between the low, medium, and high power coils are therespective gauges of the coil. Although described in connection withcoils, the primary coil assembly 222 may alternatively be essentiallyany structure capable of selectively generating multiple ranges of powerusing electromagnetic fields. In one embodiment, the primary coilassembly 222 may be implemented as multiple printed circuit board coils,such as a printed circuit board coil incorporating the inventiveprinciples of U.S. Ser. No. 60/975,953, which is entitled “PrintedCircuit Board Coil” and filed on Sep. 28, 2007 by Baarman et al, andwhich is incorporated herein by reference in its entirety.

The circuit diagram of FIG. 8 illustrates an exemplary switching circuit802 and tank circuit 804. The switching circuit includes two fieldeffect transistor switches 810, 812. However, essentially any type ofswitches may be used. The switches 810, 812 convert DC power to ACpower. The AC power is fed in parallel to three switched LC circuits. Inthe current embodiment, each LC circuit includes a variable capacitor814, 816, 818 that sets the starting resonance for each coil. In analternative embodiment, the variable capacitors 814, 816, 818 may bedeleted or replaced with non-variable capacitors. The variablecapacitors 814, 816, 818 may be controlled my controller 202 duringoperation or manually at the time of manufacture. In the illustratedembodiment, the primary coil assembly includes a low power coil, 832, amedium power coil 834 and a high power coil 836. However, as previouslydiscussed, different configurations and different numbers of coils maybe implemented. Switches 820, 822, 824, 826, 828, 830 control which coil832, 834, 836 receives power and therefore, which coil or coils areenergized. In the current embodiment, the controller 302 activates onepair of switches 820-822, 824-826, 828-830 at a time. That is, the coilsare activated in a mutually exclusive fashion. However, in alternativeembodiments, multiple coils may be activated simultaneously depending onthe application. Further, in other alternative embodiments, additionalswitches could be placed between each coil for a matrix selection. Inanother alternative embodiment, switches 822, 826, 830 are deleted orshorted in order to reduce the number of switches in the circuit.

In the current embodiment, the wireless IR receiver 212 and currentsensor circuit 210 are both used for communication with remote devices.The current sensor 210 may be used to sense reflected impedance from theremote device, which effectively allows communication over the inductivecoupling. The wireless IR receiver may be used to communicate with thewireless IR transmitter 320 in the secondary circuit 300. In analternative embodiment, a peak detector may replace or be used inconjunction with the communication system already in place. One or bothof wireless IR receiver 212 and current sensor circuit 210 may bereplaced with a different communication system for communicating withone or more remote devices. For example, any of WIFI, infrared,Bluetooth, cellular or RFID communication systems may be implemented inthe primary circuit 200. In one embodiment, the current sensor circuitreceives power demand information relating to remote devices with lowerpower classes and the wireless IR receiver receives power demandinformation relating to devices with higher power classes. Communicatingusing the current sensor circuit can be inefficient where a higheramount of power is being transferred. By using a different communicationsystem during higher power transfer, losses can be decreased.

In operation, the primary controller 202, driver circuit 204 andswitching circuit 206 apply alternating current to the tank circuit 208to generate a source of electromagnetic inductive power at a selectedpower range and frequency.

One embodiment of a tank circuit 208 is illustrated in FIG. 4, andgenerally designated 400. The tank circuit 208 includes a coil selectorcircuit 420 and a primary coil assembly 408. The primary coil assembly408 includes an optional positioning magnet 420, a low power coil 410, amedium power coil 412 and a high power coil 414. In the currentembodiment, some of the coils share electrical connections to the coilselector circuit. Specifically, the low power coil 410 shares a leadwith the medium power coil 412. The medium power coil 412 shares adifferent lead with the high power coil 414.

The physical characteristics effect the power that is transferred whenthe coil is energized. Examples of such characteristics includegeometry, length, gauge, and number of turns. Essentially any of thephysical characteristic of the coils 414, 412, 410 may vary. In theillustrated embodiment, the low power coil 512 has a relatively shortlength and gauge compared to the medium power coil 514, which in turnhas a shorter length and gauge than the high power coil 514. Further,the coils depicted in FIG. 4 are generally circular. However, the coilsmay be implemented using other shapes, such as oval, rectangular,square, to list a few. In one embodiment, multidimensional coils areimplemented.

Other factors can also effect the power transferred when the coil isenergized. For example, one factor is the spacing between the coils 410,412, 414. In the embodiment illustrated in FIG. 4 there are gaps 416,418 between the coils 410, 412, 414 that can potentially reducecross-talk or other interference. In the current embodiment, these gaps416, 418 are filled with air and serve to provide some isolation betweenthe coils 410, 412, 414. In an alternative embodiment, the gaps 416, 418may be filled with a shielding material to provide additional isolation.In another alternative embodiment, the gaps 416, 418 may be filled withferrite in order to direct the magnetic fields produced by coils 410,412, 414. In the embodiment illustrated in FIG. 6, the spacing betweenthe coils 610, 612, 614 is limited. There are no gaps between the coils,which allows the coils to be more compact while maintaining their size.In the FIG. 6 embodiment, the coils share some leads to the coilselector circuit 620. In alternative embodiments, each coil 610, 612,614 may include two separate leads to the coil selector circuit 620.

IV. Remote Device

One embodiment of a secondary circuit is shown in FIG. 3, and generallydesignated 300. In the embodiment illustrated in FIG. 3, the secondarycircuit 300 generally includes a secondary 302, rectifier 304 (or othercomponents for converting AC power to DC), a secondary controller 316,memory 322, a wireless IR transmitter 320, a signal resistor 318, and aload 306. Other circuitry may be included. For example, in onealternative embodiment a low voltage power supply may be included toscale the received power. In another alternative embodiment,conditioning circuitry may be included to filter or otherwise conditionthe received power.

The secondary coil 302 of the of the illustrated embodiment is a coil ofwire suitable for generating electricity when in the presence of avarying electromagnetic field. Perhaps as shown best in FIG. 5, thesecondary coil 509 may correspond in size and shape to one of theprimary coils 512, 514, 516. For example, the two coils may havesubstantially equal diameters. In some applications, the secondary coil509 may be a coil of Litz wire. As with the primary coils, thecharacteristics of the secondary coil 509 may vary from application toapplication. For example, the number of turns, size, shape,configuration or other characteristics of the secondary coil 509 mayvary. Further, the characteristics of the wire may vary, such as length,gauge and type of wire. Although described in connection with a coil ofwire, the secondary coil 509 may alternatively be essentially anystructure capable of generating sufficient electrical power in responseto the intended electromagnetic field.

In some alternative embodiments the remote device may have multiplesecondary coils. For example, the remote device may have a separate lowpower coil for low power applications and separate medium and high powercoils for medium and high power applications. In another alternativeembodiment, the remote device has multiple secondary coils to give theremote device orientation and spatial freedom.

In one embodiment, multiple secondary coils receiving power of differentphases can be used to reduce the ripple voltage. This is referenced inApplication 60/976,137, entitled “Multiphase Inductive Power SupplySystem” filed Sep. 9, 2007 to Baarman et al, which is hereinincorporated by reference. Multiple coil assemblies each with multiplecoils may be desired to transmit power at different phases in such anembodiment.

In operation, the rectifier 304 converts the AC power generated in thesecondary coil 302 to DC power. In some applications the rectifier maybe deleted. For example, if the load 306 accepts AC power.

The secondary controller 316 may be essentially any type ofmicrocontroller that is capable of operating the communication system tocommunicate power demand information to the inductive power supply. Insome embodiments the secondary controller 316 includes memory. In theillustrated embodiment, the secondary circuit includes external memory322. The memory generally includes power demand information and mayinclude additional information about the remote device. The power demandinformation may include a power class that categorizes how much powerthe remote device desires.

In one embodiment, there are three power classes: the low power class,the medium power class and the high power class. The low power class isdefined as devices that desire between 0 and 5 watts of power. Themedium power class is defined as devices that desire between 5 and 110watts of power. The high power class is defined as devices that desiremore than 110 watts of power. Examples of devices categorized as lowpower class devices under this power class scheme include cell phones,MP3 players and personal digital assistants (PDA). Example of deviceswith a medium power class include laptop computers and other mediumpower applications. Examples of high power devices include kitchenappliances, such as a blender or frying pan. In alternative embodiments,with different power class schemes the definitions of the power classesmay vary.

In one embodiment, signal resistor 318 may be used to send informationto the primary controller 202. The use of a signal resistor 318 toprovide communication from the secondary circuit 103 to the primarycircuit 105 was discussed in U.S. patent application Ser. No.11/855,710, which was previously incorporated by reference. The signalresistor 318, when shunted, sends a communication signal that signifiesan over-current or over-voltage state. When the resistor is shunted, thecurrent or peak detector on the primary circuit 103 is able to sense theover-voltage/over-current condition and act accordingly. The signalresistor 318 of the present invention may be shunted systematically tocommunicate additional data to the primary controller 202. For example,a stream of data could represent power demand information or provideother information about the remote device. Alternatively, the signalresistor 318 could be replaced with a different communication systementirely. For example, wireless transmitter 320 may be used inconjunction with or in lieu of signal resistor 318 to wirelesslycommunicate with the wireless receiver 212 of the primary circuit 200.In an alternative embodiment, one or both of wireless IR transmitter 320and signal resistor 318 may be replaced with a different communicationsystem for communicating with the inductive power supply. For example,any of WIFI, infrared, Bluetooth, cellular or RFID communication systemsmay be implemented in the remote device 104.

Use of a wireless transmitter or transceiver was previously described inU.S. Patent Application Publication US 2004/130915A1 to Baarman, whichwas previously incorporated by reference. Specifically, the use of WIFI,infrared, Bluetooth, cellular or RFID were previously discussed as waysto wirelessly communicate data between a remote device to an inductivepower supply. Further, communication using the induction coils and apower line communication protocol was discussed. Any of these methods oftransmitting data could be implemented in the present invention in orderto transfer the desired data from the remote device to the inductivepower supply.

The remote device load 306 may essentially any suitable load. In someembodiments, the load 306 may be a rechargeable battery and thesecondary circuit may include additional charging circuitry. In otherembodiments the load 306 may relate to the function of the remotedevice.

V. Method

A method for authentication and power transfer control is illustrated inthe flowchart of FIG. 9, and generally designated 900. The methodincludes periodically transmitting ping messages 902, authenticating anymessages received in response 904, in response to an authentic message,determining the control identification class (CIDC) and primary powerclass (PPC) and initiating power transfer based on the determined CIDCand PPC 906. During active power transfer mode 908, the presence of thedevice and the status of the control point is continually checked 910 ina feedback loop with control feedback packets from the remote device912.

In one embodiment, the inductive power supply is in one of severalmodes: pinging or active power transfer. The ping mode activelydetermines if a qualified device is present. Power transfer only takesplace when a device identification class is recognized and validated.

A safe ping frequency may be determined using the characteristics of thehardware in the inductive power supply system. The primary attemptscommunication with a secondary by energizing the low power (or other)coil at a specified ping frequency and waits for a response. If asecondary is present within the charging zone, it may be poweredsufficiently by the energy sent during the ping operation to initializeitself and send an identification message that may contain power demandinformation to the inductive power supply.

If the primary fails to detect a device in the charging field during theping operation, the coil power is removed until the next attempt fordetection. If a device is detected during the ping operation, theprimary reverts to the established initial operating frequency in anattempt to begin power transfer. The power delivered to the secondaryduring transfer may be controlled based upon communications receivedfrom the secondary.

The control identification classes may identify different controlmethods for the inductive power supply to use to charge or power theremote device. Examples of control identification classes includecharging set point control, charging error control, power supply setpoint control, power supply error control and power supply directcontrol.

The primary power class determines the range of power of a specific coilof the inductive power supply. The primary power class also may impactthe coil geometry and parametric specifications. In an alternativeembodiment, the primary power class includes information about theentire range of power provided by the inductive power supply. The remotedevice may include a remote device power class in the power demandinformation transmitted to the inductive power supply. The remote devicepower class and the primary power class may be one in the same, or theymay be different.

In one embodiment, the power class is a portion of the informationcommunicated from the remote device to inductive power supply. In oneembodiment information may be provided to the primary circuit about themaximum amount of power the remote device can be expected to require.For example, a cell phone may fall under a 3.5 W maximum power level.Its power class byte would be 0000 0111 b.

The following chart describes how a power class byte may be constructed.The power class may be encoded in essentially any manner, this chartmerely represents one possible embodiment.

TABLE 1 Power Class Bits Power Class Bits [7:6] Multiplier [5:0] PowerLevels (W) 00 1 00000-11111 0-32 W, 0.5 W Increments 01 10 00000-111110-320 W, 5 W Increments 10 100 00000-11111 0-3200 W, 50. W Increments 111000 00000-11111 0-32000 W, 500 W Increments

FIG. 10 illustrates a functional block diagram for providing power inaccordance with one embodiment of the present invention. FIG. 11illustrates a functional block diagram for receiving power in accordancewith one embodiment of the present invention. FIG. 12 illustrates afunctional block diagram for providing power in accordance with anotherembodiment of the present invention. FIG. 13 illustrates a functionalblock diagram for receiving power in accordance with one embodiment ofthe present invention.

The functional block diagrams of FIGS. 10 and 11 are directed toinductively charging a load in a remote device. The functional blockdiagrams of FIGS. 12 and 13 are directed to inductively charging arechargeable battery in a remote device.

In FIG. 10 and FIG. 12, each of the coils may represent a primary coilassembly with multiple coils as described above. Alternatively, each ofthe coils may represent one coil of a primary coil assembly.

Above, several embodiments of multiple coil inductive power supplieshave been described. Specifically, examples have been provided ofmultiple coil inductive power supplies that use multiple coilsconfigured in a multi-tap configuration and multiple coil inductivepower supplies that use a separate coil configuration. Otherconfigurations that provide variable inductance may also be provided.For example, a segmented primary, such as the Litz wire coil shown inFIG. 15, may provide multiple strands that can be connected andenergized in various configurations to provide a variable amount ofinductance. The various configurations of the segmented primary allowthe inductive power supply to better match secondary power and couplingrequirements from high power to low power levels using the same primary.In the current embodiment, the combination of taps and segmentconfigurations provides a wide range of inductance values and wiregauges. In some embodiments, some of the segments may be disconnected,allowing an even wider range.

Depending on how the strands are connected, different configurations maybe created. The table below describes a number of examples of variouscoil selection circuit segment options.

TABLE 2 Initial Realized Realized Turns Segments Awg. ConfigurationTurns 10 4 X 4-Parallel 10 10 4 X/2 2-Parallel & 2- 20 Series 10 4 X/44-Series 40

FIG. 15 shows a cross section of litz wire that has been segmented intofour sections. In the illustrated embodiment, each section may beenergized individually. In an alternative embodiment, the sections maybe divided differently, or each strand may be energized separately.Further, in the current embodiment, the coil selector circuit connectsto each segment separately at each tap so that the segments can bearranged in parallel or series depending on how the coil selectorcircuit connects the various segments together.

Although FIG. 15 illustrates three coils 610, 612, 614 of varyinggauges. In an alternative embodiment, each coil may be the same gauge,and the gauge may be controlled by the coil selector circuit choosingwhich segments or individual strands to energize.

As described above in connection with the other inductive power supplyembodiments, the coil selector circuit may be controlled according to aprogram residing in memory in the controller 202. The coil selectorcircuit may change the configuration of the segmented primary duringoperation to adjust based on power demand information provided from theremote device. The ability to dynamically change the gauge of the wire,and other characteristics, is useful to better match the secondary powerand coupling requirements.

The above description is that of the current embodiment of theinvention. Various alterations and changes can be made without departingfrom the spirit and broader aspects of the invention.

1. An inductive power supply for supplying wireless power to a remotedevice including power demand information, said inductive power supplycomprising: a plurality of tank circuits, wherein each tank circuitincludes a primary and a capacitor electrically connected in series,wherein each of said plurality of tank circuits are capable of beingenergized to transfer power wirelessly to the remote device; a receiverfor receiving power demand information from the remote device; and acontroller in electrical communication with said receiver and saidplurality of tank circuits, said controller programmed to select atleast one of said plurality of tank circuits to transfer powerwirelessly to the remote device, wherein said selection is determined asa function of said power demand information received from the remotedevice.
 2. The inductive power supply of claim 1 wherein said pluralityof tank circuits includes a tank circuit with a low power primary coil,a tank circuit with a medium power primary coil, and a tank circuit witha high power primary coil.
 3. The inductive power supply of claim 1wherein said primary of each of said plurality of tank circuits is adifferent gauge.
 4. The inductive power supply of claim 1 wherein saidreceiver includes at least one of a wireless communication system, atleast one of said tank circuits, or any combination thereof.
 5. Theinductive power supply of claim 1 including a coil selector circuit forselectively energizing one or more of said plurality of tank circuits.6. The inductive power supply of claim 1 wherein said power demandinformation includes a remote device ID, wherein said inductive powersupply includes a memory, wherein said memory includes a look-up table,said look-up table maps remote device IDs to at least one of saidplurality of primaries.
 7. An inductive power supply for supplyingwireless power to a remote device including power demand information,said inductive power supply comprising: a first tank circuit including aplurality of primaries, wherein each of said plurality of primaries iscapable of being energized to transfer power wirelessly to the remotedevice; a receiver for receiving power demand information from theremote device, wherein said power demand information includes a poweradjustment; and a controller in electrical communication with saidreceiver and said tank circuit, said controller programmed to select atleast one of said plurality of primaries of said tank circuit totransfer power wirelessly to the remote device, wherein said selectionis determined as a function of said power adjustment received from theremote device.
 8. The inductive power supply of claim 7 including asecond tank circuit and a third tank circuit, each including a pluralityof primaries, wherein each of said plurality of primaries of said firstand second tank circuits are capable of being energized to transferpower wirelessly to the remote device, wherein said first tank circuitincludes a low power primary coil, said second tank circuit includes amedium power primary coil, and said third tank circuit includes a highpower primary coil.
 9. The inductive power supply of claim 8 whereinsaid first, second, and third tank circuits are driven with a halfbridge driver.
 10. The inductive power supply of claim 7 wherein saidreceiver includes at least one of a wireless communication system, atleast one of said primaries, or any combination thereof.
 11. Theinductive power supply of claim 7 wherein said tank circuit includes acoil selector circuit for selectively energizing one or more of theplurality of primaries.
 12. The inductive power supply of claim 7wherein said controller is programmed to determine an amount of power tobe transmitted as a function of said power adjustment received from saidremote device.
 13. The inductive power supply of claim 12 including amemory, wherein said memory includes a threshold, said controller isprogrammed to select one of said plurality of primaries in response tosaid amount of power to be transmitted being below said threshold, andsaid controller is programmed to select a different one of saidplurality of primaries in response to said amount of power to betransmitted being above said threshold.
 14. The inductive power supplyof claim 13 wherein said power demand information includes at least oneof a minimum power level threshold, a maximum power level threshold, ora combination thereof.
 15. The inductive power supply of claim 14wherein said controller adjusts said threshold as a function of said atleast one of said minimum power level threshold, said maximum powerlevel threshold, or said combination thereof.
 16. The inductive powersupply of claim 7 wherein said remote device includes a standby modewhere it demands a lower amount of power, said power demand informationincludes an indication that said remote device is in standby mode, andsaid controller selection is based at least in part on whether saidremote device is in said standby mode.
 17. An inductive power supply forsupplying wireless power to a first remote device or a second remotedevice, said inductive power supply comprising: a tank circuit includinga first primary coil and a second primary coil, wherein said firstprimary coil and said second primary coil are arranged concentrically,wherein each of said first primary coil and said second primary coil arecapable of being energizing to transfer power wirelessly; a magnetarranged coaxially with said first primary coil and said second primarycoil, wherein said magnet provides a magnetic force to assist inalignment, wherein said magnetic force of said magnet assists inaligning the first remote device with said first primary coil andwherein said magnetic force of said magnet assists in aligning thesecond remote device with said second primary coil.
 18. The inductivepower supply of claim 17 for supplying wireless power to at least one ofa first remote device, a second remote device, and a third remotedevice: wherein said tank circuit includes a third primary coil, whereinsaid third primary coil is arranged concentrically with said first andsaid second primary coils, wherein said third primary coil is capable ofbeing energized to transfer power wirelessly; and wherein said magnet isarranged coaxially with said first primary coil, said second primarycoil, and said third primary coil, wherein said magnetic force of saidmagnet assists in aligning the third remote device with the thirdprimary coil.
 19. An inductive power supply for supplying wireless powerto at least one of a first remote device demanding a lower amount ofpower, a second remote device demanding a lower amount of power, a thirdremote device demanding a higher amount of power, and a combinationthereof, said inductive power supply comprising: a tank circuitincluding a lower power primary coil and a higher power primary coil,wherein said lower power primary coil is capable of being energized totransfer power wirelessly to at least one of the first remote devicedemanding a lower amount of power and the second remote device demandinga lower amount of power, wherein said higher power primary coil iscapable of being energized to at least one of 1) transfer powerwirelessly simultaneously to both the first remote device demanding alower amount of power and the second remote device demanding a loweramount of power, and 2) transfer power wirelessly to the third remotedevice demanding a higher amount of power; a receiver for receivingpower demand information; and a controller in electrical communicationwith said tank circuit and said receiver, said controller programmed toselect at least one of said lower power primary coil and said higherpower primary coil to transfer power wirelessly, wherein said selectionis determined as a function of said power demand information receivedfrom the remote device;
 20. An inductive power supply for supplyingwireless power to a remote device, said inductive power supplycomprising: a tank circuit including a plurality of primaries, whereineach of said plurality of primaries is capable of being energized totransfer power wirelessly to the remote device; a first receiver forreceiving power demand information from the remote device; a secondreceiver for receiving power demand information from the remote device;and a controller in electrical communication with said firstcommunication system, said second communication system, and said tankcircuit, said controller programmed to select at least one of saidplurality of primaries of said tank circuit to transfer power wirelesslyto the remote device, wherein said selection is determined as a functionof said power demand information received from at least one of saidfirst receiver said second receiver.
 21. The inductive power supply ofclaim 20 wherein said first receiver includes a primary of saidplurality of primaries and said second receiver includes a wirelesscommunication system.
 22. The inductive power supply of claim 20 whereinsaid remote device includes a power class, wherein said first receiverreceives power demand information relating to remote devices with lowerpower classes and said second receiver receives power demand informationrelating to devices with higher power classes.